In a needle roller bearing (needle bearing) that uses needle rollers as rolling bodies, numerous rollers are held by a cylindrical retainer in which pockets for accommodating the rollers are formed at a fixed pitch in a circumferential direction. In this type of retainer, the pockets open into the inner circumferential face and the outer circumferential face of the retainer, and adjacent pockets are partitioned by columnar partitions arranged in the circumferential direction.
The inner-circumferential-side openings or the outer-circumferential-side openings of the pockets are shaped so that the accommodated rollers are retained. For example, the retainer is made from a cylindrical resin, and retaining protrusions are formed in the edges of the inner-circumferential-side openings or the outer-circumferential-side openings of the pockets. With such a configuration, the protrusions can be elastically deformed by pressing force and the rollers can be pushed into the pockets. The rollers can also be prevented from dislodging because the protrusions elastically revert after being fitted into the pockets. Patent Documents 1 and 2 disclose this type of resin-formed retainer for a needle roller bearing.